The following abbreviations and terms are herewith defined, at least some of which are referred to within the following description of the present disclosure.
3GPP3rd-Generation Partnership ProjectAGCHAccess Grant ChannelASICApplication Specific Integrated CircuitBLERBlock Error RateBSSBase Station SubsystemCCCoverage ClassCCCChange Control CycleCIoTCellular Internet of ThingsCNCore NetworkDRXDiscontinuous ReceptionECExtended CoverageEC-BCCHExtended Coverage Broadcast Control ChannelEC-GSMExtended Coverage GlobalSystem for Mobile CommunicationsEC-PCHExtended Coverage Paging ChannelEC-SCHExtended Coverage Synchronization ChannelEC-SIExtended Coverage System InformationeDRXExtended Discontinuous ReceptioneNBEvolved Node BDLDownlinkDSPDigital Signal ProcessorEDGEEnhanced Data rates for GSM EvolutionEGPRSEnhanced General Packet Radio ServiceGSMGlobal System for Mobile CommunicationsGERANGSM/EDGE Radio Access NetworkGPRSGeneral Packet Radio ServiceHARQHybrid Automatic Repeat RequestIoTInternet of ThingsLTELong-Term EvolutionMCSModulation and Coding SchemeMMEMobility Management EntityMSMobile StationMTCMachine Type CommunicationsNBNode BPDNPacket Data NetworkPDTCHPacket Data Traffic ChannelRACHRandom Access ChannelRANRadio Access NetworkRATRadio Access TechnologySGSNServing GPRS Support NodeSISystem InformationTDMATime Division Multiple AccessTSTechnical SpecificationsUEUser EquipmentULUplinkWCDMAWideband Code Division Multiple AccessWiMAXWorldwide Interoperability for Microwave AccessCoverage Class (CC): At any point in time a mobile station belongs to a specific uplink/downlink coverage class that corresponds to either the legacy radio interface performance attributes that serve as the reference coverage for legacy cell planning (e.g., a Block Error Rate of 10% after a single radio block transmission on the PDTCH) or a range of radio interface performance attributes degraded compared to the reference coverage (e.g., up to 20 dB lower performance than that of the reference coverage). Coverage class determines the total number of blind transmissions to be used when transmitting/receiving radio blocks. An uplink/downlink coverage class applicable at any point in time can differ between different logical channels. Upon initiating a system access a mobile station determines the uplink/downlink coverage class applicable to the RACH/AGCH based on estimating the number of blind transmissions of a radio block needed by the BSS (radio access network node) receiver/mobile station receiver to experience a BLER (block error rate) of approximately 10%. The BSS determines the uplink/downlink coverage class to be used by a mobile station on the assigned packet channel resources based on estimating the number of blind transmissions of a radio block needed to satisfy a target BLER and considering the number of HARQ retransmissions (of a radio block) that will, on average, be needed for successful reception of a radio block using that target BLER. Note: a mobile station operating with radio interface performance attributes corresponding to the reference coverage (normal coverage) is considered to be in the best coverage class (i.e., coverage class 1) and therefore does not make any additional blind transmissions subsequent to an initial blind transmission. In this case, the mobile station may be referred to as a normal coverage mobile station. In contrast, a mobile station operating with radio interface performance attributes corresponding to an extended coverage (i.e., coverage class greater than 1) makes multiple blind transmissions. In this case, the mobile station may be referred to as an extended coverage mobile station. Multiple blind transmissions correspond to the case where N instances of a radio block are transmitted consecutively using the applicable radio resources (e.g., the paging channel) without any attempt by the transmitting end to determine if the receiving end is able to successfully recover the radio block prior to all N transmissions. The transmitting end does this in attempt to help the receiving end realize a target BLER performance (e.g., target BLER≤10% for the paging channel).
DRX cycle: Discontinuous reception (DRX) is a process of a mobile station disabling its ability to receive when it does not expect to receive incoming messages and enabling its ability to receive during a period of reachability when it anticipates the possibility of message reception. For DRX to operate, the network coordinates with the mobile station regarding when instances of reachability are to occur. The mobile station will therefore wake up and enable message reception only during pre-scheduled periods of reachability. This process reduces the power consumption which extends the battery life of the mobile station and is sometimes called (deep) sleep mode.
Extended Coverage: The general principle of extended coverage is that of using blind transmissions for the control channels and for the data channels to realize a target block error rate performance (BLER) for the channel of interest. In addition, for the data channels the use of blind transmissions assuming MCS-1 (i.e., the lowest modulation and coding scheme (MCS) supported in EGPRS today) is combined with HARQ retransmissions to realize the needed level of data transmission performance. Support for extended coverage is realized by defining different coverage classes. A different number of blind transmissions are associated with each of the coverage classes wherein extended coverage is associated with coverage classes for which multiple blind transmissions are needed (i.e., a single blind transmission is considered as the reference coverage). The number of total blind transmissions for a given coverage class can differ between different logical channels.
Internet of Things (IoT) devices: The Internet of Things (IoT) is the network of physical objects or “things” embedded with electronics, software, sensors, and connectivity to enable objects to exchange data with the manufacturer, operator and/or other connected devices based on the infrastructure of the International Telecommunication Union's Global Standards Initiative. The Internet of Things allows objects to be sensed and controlled remotely across existing network infrastructure creating opportunities for more direct integration between the physical world and computer-based systems, and resulting in improved efficiency, accuracy and economic benefit. Each thing is uniquely identifiable through its embedded computing system but is able to interoperate within the existing Internet infrastructure. Experts estimate that the IoT will consist of almost 50 billion objects by 2020.
Cellular Internet of Things (CIoT) devices: CIoT devices are IoT devices that establish connectivity using cellular networks.
Machine Type Communication (MTC) devices: A MTC device is a type of device where support for human interaction with the device is typically not required and data transmissions from or to the device are expected to be rather short (e.g., a maximum of a few hundred octets). MTC devices supporting a minimum functionality can be expected to only operate using normal cell contours and as such do not support the concept of extended coverage whereas MTC devices with enhanced capabilities may support extended coverage.
At the Third Generation Partnership Project (3GPP) Technical Specification Group (TSG) GSM/EDGE Radio Access Network (GERAN) meeting #67, a new work item entitled “New Work Item on Extended Coverage GSM (EC-GSM) for support of Cellular Internet of Things” (CIoT) was discussed and approved in GP-151039 (dated: Aug. 10-14, 2015) with the intention to improve coverage with 20 dB, to improve device battery life time, and to decrease device complexity. The contents of GP-151039 are hereby incorporated herein by reference for all purposes.
Extended coverage (i.e., a coverage range beyond that of legacy General Packet Radio Service (GPRS)/Enhanced GPRS (EGPRS) operation) is achieved by blind physical layer repetitions in both uplink (UL) and downlink (DL), where the number of repetitions is associated with a given Coverage Class (CC). Logical channels supporting operation in extended coverage are referred to as Extended Coverage (EC)-channels. Four different Coverage Classes are defined in the ongoing 3GPP standardization work, each Coverage Class approximated with a level of extended coverage range compared to legacy GPRS/EGPRS operation, which are denoted as CC1, CC2, CC3 and CC4 respectively. More specifically, CC1 corresponds to the coverage range of legacy GPRS/EGPRS operation (i.e., extended coverage and blind repetitions not used). CC2 has four blind repetitions for the EC-RACH, EC-PDTCH and EC-PACCH, and eight blind repetitions for the EC-PCH and EC-AGCH. CC3 has sixteen blind repetitions for the EC-RACH, eight blind transmissions for the EC-PDTCH and EC-PACCH, and sixteen blind repetitions for the EC-PCH and EC-AGCH. CC4 has forty-eight blind transmissions for the EC-RACH, 16 blind repetitions for the EC-PDCTH and EC-PACCH, and thirty-two blind transmissions on the EC-PCH and EC-AGCH.
For some logical channels, the number of blind physical layer repetitions can vary depending on the coverage extension required. But for the Extended Coverage Broadcast Control Channel (EC-BCCH), which carries all the system information (SI) needed for the Mobile Station (MS)/CIoT device to gain access to the Extended Coverage Global System for Mobile (EC-GSM) communications system, the number of blind physical layer repetitions is always fixed to 16 (i.e., in order to reach mobile stations in extended coverage corresponding to the highest Coverage Class (CC4), each EC-BCCH block comprising a complete or a segment of an EC-SI message is always repeated over 16 consecutive 51-multiframes).
In the current standardization work for EC-GSM, four system information (SI) messages are defined, denoted as EC-System Information Type 1 (EC-SI 1), EC-System Information Type 2 (EC-SI 2), EC-System Information Type 3 (EC-SI 3) and EC-System Information Type 4 (EC-SI 4).
The EC-SI messages are either sent on a single EC-BCCH block per 51-multiframe (known as EC-BCCH Normal) or optionally on two EC-BCCH blocks per 51-multiframe (the second EC-BCCH block is known as EC-BCCH Extended). Each EC-S1 message is repeated over 16 consecutive EC-BCCH blocks in 16 consecutive 51-multiframes in a Round Robin scheme. An example of EC-System Information (EC-SI) message transmission is provided below in TABLE #1.
TABLE #151-multiframeEC-BCCH normalEC-BCCH ExtendedN + 0-N + 15EC-System Information 1EC-System Information 2N + 16-N + 31EC-System Information 3EC-System Information 4N + 32-N + 47EC-System Information 1EC-System Information 2N + 48-N + 63EC-System Information 3EC-System Information 4N + 64-N + 79EC-System Information 1EC-System Information 2. . .. . .. . .. . .. . .. . .
The signaling in TABLE #1 is just one example of how to broadcast EC-System Information in a cell. If BCCH Extended is not activated in the cell, then all EC-SI messages (EC-SI 1-EC-SI 4) will instead be sent on the EC-BCCH Normal block in a Round Robin scheme.
The EC-SI is broadcasted in each cell within the EC-GSM system, carrying network related information such as network identity parameters, cell selection parameters, power control parameters, neighbor cells, etc. When the mobile station (MS) enters a new cell at e.g., power on or at cell re-selection, the MS needs to read the complete EC-System Information set (i.e., all EC-SI messages) before accessing the cell.
Discontinuous Reception (DRX) is a power saving technique that allows the MS to power down for a certain period of time while being in idle mode. The period of time when the MS is powered down is commonly called the “sleep mode”. When the MS wakes up from “sleep mode” according to its DRX cycle (e.g. if the MS uses a DRX cycle of 26 minutes, it wakes up once every 26 minutes) in the same cell as the one in which it previously read the complete EC-System Information, the MS needs to read an EC-SI change mark indicator included in the EC-Synchronization Channel (EC-SCH) before accessing the cell (EC-SCH is a logical channel transmitted on the same carrier as the EC-BCCH providing information such as frequency and base station identity). The EC-SI change mark indicator is a 2-bit field with a value range from 0 to 3 that is stepped whenever the network changes the content of an EC-SI message. If the value of the EC-SI change mark indicator is unchanged since the last time the indicator was read, the MS concludes that the content of the EC-SI message set has not been changed. But if the MS detects a change to the EC-SI change mark indicator when reading the EC-SCH, then the MS understands that the content of at least one EC-SI message has changed, thus the MS needs to re-read all the EC-SI messages in the cell before accessing the network.
The problem with the existing solution is that the change of the EC-SI change mark indicator field in the EC-SCH does not indicate which specific EC-SI message has been changed, i.e., the MS needs to read the complete EC-SI message (EC-SI 1-EC-SI 4) set regardless if only the content of one EC-SI message is in fact changed.
The time period during which the network can change the content of the EC-System Information (up to a certain maximum number of times) without overflowing the EC-SI change mark indicator, is here defined as the EC-SI Change Control Cycle. The length of the EC-SI Change Control Cycle is effectively selected by the network and serves as the time interval during which the network intends to avoid changing the EC-System Information more often than a certain maximum number of times (e.g., if the EC-SI Change Control Cycle is 24 hours long the network avoids overflowing the EC-SI change mark indicator by not changing the EC-System Information more often than 3 times during that time period).
In general, it is an advantage if the MS can avoid reading the complete EC-System Information message set (EC-SI 1-EC-SI 4) too frequently. This is not only due to the network access delay when the MS needs to re-read the complete EC-SI message set (the time required for reading four EC-SI messages on EC-BCCH Normal is approximately 16 seconds for an MS using the worst coverage class (CC4), assuming one EC-BCCH block carries one complete EC-SI message), the MS will also waste valuable battery power when acquiring and decoding EC-SI messages that are in fact unchanged, thus always reading the complete EC-SI message set (EC-SI 1-EC-SI 4) will have a negative impact on the MS's battery life time. These problems and other problems are addressed by the present disclosure.